Method of manufacturing basic bessemer steel.



UNITED STATES PATENT OFFICE.

SAMUEL MCDONALD, OF YOUNGSTOWN, OHIO.

METHOD OF MANUFACTURING BASIC'BESSEMER STEEL.

SPECIFICATION forming part of Letters Patent No. 706,089, dated August5, 1902.

Application filed January 28, 1902. Serial No. 91,625. (No specimens.)

To all whom it may concern:

Be it known that I, SAMUEL MCDONALD, a citizen of the United States,residing at Youngstown, in the county of Mahoning and State of Ohio,have invented or discovered a certain new and useful Improvement inMethods of Manufacturing Basic Bessemer.

Steel, of which improvement the following is a specification.

This invention relates to the removal of phosphorus from the charge of aBessemer converter-that is, to the production of basic Bessemersteel-and has for its object to enable the operator to perform thatprocess more expeditiously than it has been performed heretofore. Insecuring this object in the manner hereinafter described the operator isenabled also to obtain a product of better and more uniform qualitythan-can be obtained by the method now generally adopted and to controlthe temperature of the metal at the time of casting.

The process of making basic Bessemer steel which has heretoforeprevailed is substantially this: The Bessemer vessel is lined withmagnesian lime, a quantity of well burnt lime is placed in the bottom ofthe vessel, and the metal which is to be converted is introduced inmolten condition. The charge is then blown in the ordinary manner untilthe carbon is eliminated, this stage being indicated by the drop of thecarbon-flame. Instead of terminating the blow on the drop of thecarbon-flame, which is the practice in making ordinary or acid Bessemersteel, the blow is continued for an interval of time, which is termedthe afterblow. During this interval the reaction between the charge andthe basic substances within the converter continues and brings about thesubstantial elimination of phosphorus and other foreign substances,which elimination constitutes the production of basic steel.Spiegeleisen or ferromanganese is then added, as in the ordinaryBessemer process, and the finished steel is then cast. The process thusdescribed is attended with practical difficulties of such magnitude thatit is not to-day a commercial success. One difficulty is to determinethe duration of the afterblow. While the substantial removal of carbonis clearly indicated by the drop of the flame in the mouth of theconverter, there is no pronounced indication of the substantial removalof phosphorus. It is necessary, therefore, to make tests of each chargewhen the operator judges the afterblow to have continued for sufficienttime, and if the amount of phosphorus is still too great the blow mustbe renewed. Such testing and blowing again consume time and retard theproduction. Another defect is due to variationsin the temperature of thecharge on the completion of the process, these variations being due todelays which are occasioned by testing, reblowing, and repairing theconverter-lining, for to obtain the best results the steel should becast at a temperature slightly above a certain minimum. Another defectis due to the fact that when spiegeleisen or ferromanganese isintroduced into the metal in the converter or ladle it tends to reactwith the slag and to effect a reintroduction of phosphorus into thecomposition of the metal.

My improvement consists in providing a receiving tank or furnace ofsufficient size to contain at one time the charges from a number ofconverters. Into this tank I pour the charge of each converter, and fromit I take the metal for casting. I test each converter charge in turn,as in the former practice; but instead of holding each charge subject tothe result of the test and renewing the blow if too much phosphorusremains I turn the charge without delay into the receiving-tank anddetermine the treatment of the next succeeding charge by the result ofthe test of the charge which has preceded it. Thus if the test of agiven charge reveals the presence of too much phosphorus, though I havealready introduced that charge into the receiving-tank, I continue thetreatment of the next charge not only for such time as is deemedsufficient to reduce to the proper degree its phosphorus element, butfor an additional time, and I thereby eliminate so much phosphorus fromthat charge that when it shall be introduced into the receiving-tank thephosphorus element of the entire contents of the tank shall not exceedthe proper amount. It is obvious that instead of testing each charge asit goes'to the receivingtank I may test the contents of the tank afterthe introduction of each converter charge and determine the treatment ofsucceeding converter charges by the results of these By adopting thismethod of treatment I avoid the delay incident to the former prac tests.

It will be understood that in practicing my invention I may either beginto withdraw metal from the" receiving-tank after it has been filled andcontinue to' withdraw metal until it is again empty or I may keep addingnew converter charges while withdrawing metal for casting. I find itdesirable to have two receiving-tanks, such as I have described inconnection with a Bessemer plant, and to draw from one while filling theother. By employing the receiving-tank I am able to remove thephosphorus-containing slag before the introduction of spiegeleisen orferromanganese, and I may thus avoid any deleterious edects of chemicalaction of the slag upon these substances.

I claim as my invention 1. In the manufacture of basic Bessemer steel,the method herein described,which consists in pouring successiveconverter charges into a common receptacle from which the metal is takento be cast, testing each charge in turn, and varying the duration ofeach succeeding blow according to the result of i he preceding test,substantially as described.

2. Inthe. manufacture of basic Bessemer steel, the method hereindescribed, which consists in blowing a moderate percentage of the totalproduct to be produced in suitable manner for the elimination ofphosphorus so far as may be, charging the same into a heatmaintainingreceptacle of capacity suitable to hold the entire amount of productdesired, taking a test thereof, blowing another moderate percentage ofthe total product and continuing the afterblow for such length of timethat when mixed with the charge previously blown, the phosphorus element'of the mixture will be at the desired low degree, charging this secondmoderate percentage into the receptacle and continuing such testing andfurther blowing, regulating each successive blow by the results of theprevious test until the desired quantity is produced, substantially asdescribed.

3. In the manufacture of basic Bessemer steel, the method hereindescribed, which consists in subjecting successive charges to basicBessemer treatment, testing each charge in turn and varying the durationof the treatment of succeeding charges according to the results of thepreceding tests, pouring the charges so treated into areceiving-furnace, and bringing the metal contained in the furnace to acasting temperature, substantially as described.

In testimony whereof I have hereunto set my hand.

I SAMUEL MCDONALD.

Witnesses:

DARWIN S. WOLCOTT, F. E. GAITHER.

